“Our cakes are not only famous in this area,” Lien said. “Many Vietnamese across the country as well as Vietnamese abroad order our cakes."

Lien said that every August, the village opens a training class on food hygiene for locals, where lecturers from the province’s Department of Industry and Trade teach people about the importance of clean food. After three days of training, trainees have to sit a test.

“Only people who pass the test get a certificate and are allowed to continue making banh chung,” Lien said.

According to Ngo Tien Sy, who owns the Sy Oanh Banh chung Shop, the cakes were all handmade, and locals did not use frames to wrap the cakes like in other areas.

“That’s why the quality and appearance of the cakes depends on skills of the cooks,” he said.

“If the cakes are wrapped tightly in leaves, they maintain their shape while being cooked,” he said. “The cakes look good while the sticky rice inside is soft, sticky and sweet.”

It takes 8-10 hours to boil the cakes, and during that time, the cooks have to continue adding water to ensure they don't go dry.

Sy said ingredients were bought from trustworthy suppliers who ensured the ingredients’ quality and origins.

The sticky rice comes from Bac Kan province or Hung Yen province.

Pork is marinated with pepper before it is stuffed inside layers of sticky rice and green beans. Locals use green dong (Phrynium) leaves from a nearby forest to wrap the cakes.

The water used is taken from a spring behind the village, which is believed to be holy.

Holy water is believed to provide a special taste for the delicacy.

“When they're boiled with water from the mountain, the cakes have a unique flavour,” Lien said.

Locals say Nguyen Thi Xuan, also known as Dang following her husband’s name, was the first person to make the cakes here. She opened her first shop in 1960, which quickly allured a lot of local customers.

She handed down the craft down to her children and grandchildren in her older years, and gradually, the trade has become the main source of income for the village.